The aliphatic and aromatic aldehydes are known to be very reactive. In addition to being fairly readily oxidized to the corresponding acids and reduced to the alcohols, the aldehydes enter into a number of condensation reactions, such as with amines, with alcohols, and with the same or with different aldehyde compounds. These reactions need not be described here in detail since they are well known. See, for example, ENCYLOPEDIA OF CHEMICAL TECHNOLOGY, Third Edition, Volume 1, pp. 97-112 (acetaldehyde); pp. 112-123 (acetal resins); pp. 790-798 (aldehydes); and Volume 11, pp. 231-249 (formaldehyde); John Wiley & Sons, New York. The contents of these sections are incorporated herein by reference as background material.
A number of the simpler aldehyde condensation reactions are known to be reversible under appropriate conditions. A familiar example is that of aqueous formaldehyde stabilized with methanol, commonly known as formalin, in which the formaldehyde exists as an equilibrium mixture of methylene glycol, its oligomers and hemiacetals. Another example is paraldehyde (CH.sub.3 CHO).sub.3, the cyclic trimer of acetaldehyde. This condensation product, unlike acetaldehyde, does not resinify when treated with sodium hydroxide and it does not reduce silver nitrate. However, on distilling with dilute sulfuric acid, or even on heating with water, it reverts to acetaldehyde.
Formaldehyde is the most important industrially used aldehyde. Major applications include the manufacture of phenolic resins, urea resins, acetal resins, adhesives for plywood, leather, carpet, and the manufacture of protective and decorative coatings. Also of note are formaldehyde-derived biocides such as are used in metalworking oils, coatings, fuel oil, and formaldehyde-derived pharmaceuticals.
Although it has been reported that all aldehydes are toxic, with the lower, more volatile members being considered dangerous, it was only about five years ago that the mutagenic potential of formaldehyde was recognized. See, for example, "Report of the Federal Panel on Formaldehyde", ENVIRONMENTAL HEALTH PERSPECTIVES, Vol. 42, pp. 139-168, 1982, the contents of which are incorporated herein by reference for background. Recent studies have also shown formaldehyde to be carcinogenic. Very recent reports suggest that some of the other lower aldehydes also may be mutagenic.
Recognition that formaldehyde in the environment warrants more consideration than accorded a mere nuisance, and the knowledge that many formaldehyde-derived substances, per se innocuous, may in processing or in use give rise to available formaldehyde, has led to need for a method of determining the presence of low levels of available aldehyde in a wide variety of products. Conventional analytical methods are not suitable for determining low aldehyde levels in complex mixtures which may contain interfering substances. These methods are particularly not suitable for determining whether or not all of the mutagenicity of a test article already found to be mutagenic can be ascribed to a known mutagen, e.g. formaldehyde.
It is an object of this invention to provide a biochemical method for determining the presence of available aldehyde in a test article. It is a further object to determine the presence of available formaldehyde in a test article, and to estimate its concentration. It is a still further object to provide a method for determining the presence of available aldehyde in a complex mixture that contains substances which interfere with the conventional methods for determining aldehydes. These and other objects will become apparent to one skilled in the art on reading this entire specification and the appended claims.
The term "test article" as used herein means any object or substance to be tested.
The term "available" as applied herein to aldehydes means aldehyde in free, monomeric form or in some other loosely combined form (such as formalin) which has the toxic and mutagenic properties characteristic of the free aldehyde.
The term "toxic" as used herein means the property of retarding, or completely stopping, cell growth in a culture of indicator cells.
The term "mutagenic" as used herein means the ability to induce a measureable increase in the frequency of mutation of indicator cells.
The term "assay" as used herein means mutagenicity assay.
The term "indicator cell" as used herein means a bacterial or animal cell or cell line useful for detecting mutagenicity, i.e. a cell having a defined genetic locus responsive to mutagens.